The objective of this investigation is to establish the degree of diversity of human lymphocyte subpopulations by using bacteria as markers of these subpopulations. We have developd a procedure by which the whole blood cells can be labeled with bacteria, resulting in some lymphocytes appearing surrounded by bacteria in blood smears. With this procedure, we have differentiated B cells from T cells and also two B and four T cell subpopulations. We have also found that the lymphocyte subpopulations identified by bacteria endurance are functionally different. For example, the T4 lymphocyte in our system appear to be responsible for natural killing while the T2 cell are suppressor cells for this particular function. We have also found that T1T2 cells perform specific killings of allogeneic cells and also are responsible for the mitogen response of T cells. We have investigated patients with chronic lymphocytic leukemia and found that a correlation could be established between the degree of bacterial binding to the leukemic lymphocytes and the clinical status. We now propose to study the lymphocyte subpopulations identified by bacteria adherence in patients with solid tumors. This study would be carried out in a double blind manner. We shall determine the B/T cell ratio in the peripheral blood of these patients before and after treatment, at different stages of the disease, before and after surgery, and at different time intervals after treatment. We shall determine whether the changes in the lymphocyte subpopulations in cancer patients can be correlated with a clinical status and what is the diagnostic and prognostic value of our test. We shall also follow the fate of the patients with chronic lymphocytic leukemia that have already been investigated, in terms of changes in the status and in the binding of bacteria to lymphocytes. We shall attempt to determine the possibility of automatic computerized reading of the smears developed after bacteria have been reacted with the lymphocytes, in order to obtain a test that can be used in clinical laboratories.